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Preserving an aqueous serum
I am trying to make a pretty simple and mild, oil-free serum with high molecular weight hyaluronic acid as the main gelling agent. I am currently using it 1% and I love how thick it gets. In fact everything about the serum is great EXCEPT it seems to give me a small reaction when I test it on the inside of my arm.
Normally i use Euxyl 9010 in most things but this time I am using potassium sorbate and sodium benzoate as my main preservatives with TSGD as chelating agent. I don’t usually use sodium benzoate and I’ve read that it can give this reaction to some people, so that’s my main culprit for my reaction and therefore it’s gotta go.
I don’t have many other options though because I can’t use parabens or formaldehyde donors, and although I like 9010 I am trying to avoid even phenoxyethanol in this formula.
So currently I have:
propanediol at 3%
Potassium sorbate at 0.5%
TSGD at 0.1%
PH at 5Given my unfortunate restrictions, is there anything else can I add to end up with a decent preservation system? Caprylyl glycol?
Thanks.
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5 Replies
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Phenoxyethanol is the mildest of these preservatives that you have mentioned.
Why do you want to avoid it?
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@GeorgeBenson I’d be more suspicious about Potassium sorbate, which is known to cause skin reaction. Now, the potassium sorbate/sodium benzoate system itself if not a powerful system. You could add some Benzyl alcohol and EDTA to boost it, and lower the pH a bit more.
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Both Potassium Sorbate and Sodium Benzoate (individually) can cause skin reaction in some people, so it could be either or both of these that are causing the reaction. Also, you have a high load of Potassium Sorbate … you can cut that down to 0.15%. Typical use rates are Sodium Benzoate (0.3%), Potassium Sorbate (0.15%) when used in combination.
As Abdullah mentioned, Phenoxyethanol is your best bet for mildness. But, if you are prohibited from using PE9010, you might try Pentylene Glycol (2%) + Phenethyl Alcohol (1%) + Sodium Benzoate or Potassium Sorbate at the levels I mentioned + GLDA (=TSGD)
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@MarkBroussard ahh ok i will try again with lower %’s you suggested, and then see how my skin reacts to that. Thanks.
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May I ask why you have all these preservative restrictions?? Is it fear?? While sodium benzoate/potassium sorbate are good, they are not ideal and there are better options out there.
If you stick to this system, I recommend lowering pH to 3.5-4. Prior to deciding the pH of any formula review the data for the specific preservatives. Suppliers often times have this. This way you can see what happens at different pH and the different issues you can face.
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